Correlation of seismic reflection data with seismicity over the Ramapo, New Jersey, fault zone

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Abstract

Reflection seismic data, mylonite reflectivity, gravity
data, and earthquake hypocenters have been integrated into a
possible explanation for seismicity in the Ramapo fault area.
Seven reflection seismic lines were processed using variations
in sorting and residual statics. Single VIBROSEIS
sweeps were treated as separate sourcepoints. Compressional
velocities and densities were determined in the laboratory.
Reflection coefficients and gravity models provide evidence
for reflections from mylonite zones. Earthquake hypocenters
were projected into the vertical seismic sections. The results
suggest a correlation between rock volumes containing
hypocenters and rock volumes containing mylonite zones. The
seismic line furthest from the Taconic suture displays fewer
hypocenters and mylonites, in agreement with an assumed model
of mylonite development possibly associated with obduction
of continental crust. The mylonite zones in the basement may
serve as local areas of crustal weakness for seismic activity
occurring in the area.